Our Sensei calls oyo-henka the changing of a technique mid-stream, without actually manifesting the first technique completely. For instance, ikyo to shiho-nage would mean starting the ikyo but before cutting down into the initial balance break (ie: as you "peak" the movement towards the breakover point) you change to another, in this case shiho-nage.
As apposed to henka-waza which is to do the full first break of posture in the ikyo then change.
Does this sound familiar to anyone else? I hope I am not taking his terms out of context.
Lan